package com.wutu.nbyjk8.util;

import com.aliyuncs.utils.IOUtils;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * @Author: Addons
 * @Date: 2022-04-01 17:47
 * @Desc:
 */
public class RSAUtils {


        public static String publicKeyStr ="MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCoRl/9+QidTl1LLXvNFy3AqIIYB98e23q49Hj5Vjz/0JOXf/P7RIVE8Nt6p7CNY061S9Vt2x57WZssbSk0XbSLRgiB5DFYOLn8nu4HKhTuqo+fnH0K+nidOQgeFFVKFj/N8UTti1FAlsUd3epM6BsO5mVuE/snwEh1MZlUT16mKQIDAQAB";


        public static final String CHARSET = "UTF-8";
        public static final String RSA_ALGORITHM = "RSA";


        public static Map<String, String> createKeys(int keySize){
                //为RSA算法创建一个KeyPairGenerator对象（KeyPairGenerator，密钥对生成器，用于生成公钥和私钥对）
                KeyPairGenerator kpg;
                try{
                        kpg = KeyPairGenerator.getInstance(RSA_ALGORITHM);
                }catch(NoSuchAlgorithmException e){
                        throw new IllegalArgumentException("No such algorithm-->[" + RSA_ALGORITHM + "]");
                }

                //初始化KeyPairGenerator对象,密钥长度
                kpg.initialize(keySize);
                //生成密匙对
                KeyPair keyPair = kpg.generateKeyPair();
                //得到公钥
                Key publicKey = keyPair.getPublic();
                String publicKeyStr = Base64.encodeBase64URLSafeString(publicKey.getEncoded()); //返回一个publicKey经过二次加密后的字符串
                //得到私钥
                Key privateKey = keyPair.getPrivate();
                String privateKeyStr = Base64.encodeBase64URLSafeString(privateKey.getEncoded()); //返回一个privateKey经过二次加密后的字符串

                Map<String, String> keyPairMap = new HashMap<>();
                keyPairMap.put("publicKey", publicKeyStr);
                keyPairMap.put("privateKey", privateKeyStr);

                return keyPairMap;
        }

        /**
         * 得到公钥
         * @param publicKey 密钥字符串（经过base64编码）
         * @throws Exception
         */
        public static RSAPublicKey getPublicKey(String publicKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
                //通过X509编码的Key指令获得公钥对象
                KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
                X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKey));
                RSAPublicKey key = (RSAPublicKey) keyFactory.generatePublic(x509KeySpec);
                return key;
        }

        /**
         * 得到私钥
         * @param privateKey 密钥字符串（经过base64编码）
         * @throws Exception
         */
        public static RSAPrivateKey getPrivateKey(String privateKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
                //通过PKCS#8编码的Key指令获得私钥对象
                KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
                PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey));
                RSAPrivateKey key = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
                return key;
        }

        /**
         * 公钥加密
         * @param data
         * @param publicKey
         * @return
         */
        public static String publicEncrypt(String data, RSAPublicKey publicKey){
                try{
                        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
                        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
                        return Base64.encodeBase64URLSafeString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), publicKey.getModulus().bitLength()));
                }catch(Exception e){
                        throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
                }
        }

        /**
         * 私钥解密
         * @param data
         * @param privateKey
         * @return
         */

        public static String privateDecrypt(String data, RSAPrivateKey privateKey){
                try{
                        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
                        cipher.init(Cipher.DECRYPT_MODE, privateKey);
                        return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), privateKey.getModulus().bitLength()), CHARSET);
                }catch(Exception e){
                        throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
                }
        }

        /**
         * 私钥加密
         * @param data
         * @param privateKey
         * @return
         */

        public static String privateEncrypt(String data, RSAPrivateKey privateKey){
                try{
                        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
                        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
                        return Base64.encodeBase64URLSafeString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), privateKey.getModulus().bitLength()));
                }catch(Exception e){
                        throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
                }
        }

        /**
         * 公钥解密
         * @param data
         * @param publicKey
         * @return
         */

        public static String publicDecrypt(String data, RSAPublicKey publicKey){
                try{
                        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
                        cipher.init(Cipher.DECRYPT_MODE, publicKey);
                        return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decodeBase64(data), publicKey.getModulus().bitLength()), CHARSET);
                }catch(Exception e){
                        throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
                }
        }

        private static byte[] rsaSplitCodec(Cipher cipher, int opmode, byte[] datas, int keySize){
                int maxBlock = 0;
                if(opmode == Cipher.DECRYPT_MODE){
                        maxBlock = keySize / 8;
                }else{
                        maxBlock = keySize / 8 - 11;
                }
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                int offSet = 0;
                byte[] buff;
                int i = 0;
                try{
                        while(datas.length > offSet){
                                if(datas.length-offSet > maxBlock){
                                        buff = cipher.doFinal(datas, offSet, maxBlock);
                                }else{
                                        buff = cipher.doFinal(datas, offSet, datas.length-offSet);
                                }
                                out.write(buff, 0, buff.length);
                                i++;
                                offSet = i * maxBlock;
                        }
                }catch(Exception e){
                        throw new RuntimeException("加解密阀值为["+maxBlock+"]的数据时发生异常", e);
                }
                byte[] resultDatas = out.toByteArray();
                IOUtils.closeQuietly(out);
                return resultDatas;
        }
}

